// Boost.Units - A C++ library for zero-overhead dimensional analysis and
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// unit/quantity manipulation and conversion
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//
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// Copyright (C) 2003-2008 Matthias Christian Schabel
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// Copyright (C) 2008 Steven Watanabe
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//
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// Distributed under the Boost Software License, Version 1.0. (See
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// accompanying file LICENSE_1_0.txt or copy at
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// http://www.boost.org/LICENSE_1_0.txt)
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#ifndef BOOST_UNITS_DETAIL_PUSH_FRONT_OR_ADD_HPP
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#define BOOST_UNITS_DETAIL_PUSH_FRONT_OR_ADD_HPP
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#include <boost/mpl/plus.hpp>
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#include <boost/mpl/front.hpp>
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#include <boost/mpl/push_front.hpp>
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#include <boost/mpl/pop_front.hpp>
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#include <boost/type_traits/is_same.hpp>
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#include <boost/units/units_fwd.hpp>
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#include <boost/units/detail/push_front_if.hpp>
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namespace boost {
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namespace units {
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template<class Item, class Next>
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struct list;
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namespace detail {
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template<class T>
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struct is_empty_dim;
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/// add an instantiation of dim to Sequence.
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template<bool>
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struct push_front_or_add_impl;
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template<>
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struct push_front_or_add_impl<true>
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{
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template<typename Sequence, typename T>
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struct apply
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{
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typedef typename mpl::plus<T, typename Sequence::item>::type item;
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typedef typename push_front_if<!is_empty_dim<item>::value>::template apply<
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typename Sequence::next,
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item
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> type;
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};
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};
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template<>
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struct push_front_or_add_impl<false>
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{
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template<typename Sequence, typename T>
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struct apply
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{
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typedef list<T, Sequence> type;
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};
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};
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template<typename Sequence, typename T>
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struct push_front_or_add
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{
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typedef typename push_front_or_add_impl<boost::is_same<typename T::tag_type, typename Sequence::item::tag_type>::value>::template apply<
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Sequence,
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T
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>::type type;
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};
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template<typename T>
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struct push_front_or_add<dimensionless_type, T>
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{
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typedef list<T, dimensionless_type> type;
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};
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} // namespace detail
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} // namespace units
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} // namespace boost
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#endif
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